We don’t think of the psychedelic artists of the 1960s the same way we do the abstract expressionists of the 1940s or the Impressionists who came a century before.

But an art historian can see the similarities between those unrestrained movements that defined their decades — first in Paris, then New York and after that in counterculture San Francisco. There was a style built from rebellion and reflective of broader social shifts, a new, insider language, generated as subversion but adopted as the popular culture of the day.

And there were drugs, lots of drugs, interesting drugs, and everyone took them. Though maybe that was just San Francisco, and that’s surely not the point of the exhibit, “Visual Trips,” which is making the Myhren Gallery at the University of Denver a very fun place to hang out these days.

The exhibit features scores of posters, from 1965 to 1971, advertising rock shows for such performers as the Grateful Dead, Jimi Hendrix and Jefferson Airplane. It’s one of the most complete and studied groupings of the genre ever assembled.

The era saw visual psychedelia reach new heights, and the posters indulge. There’s hardly a straight line or a clear image. Wavy, woozy, groovy, grainy stuff. Objects appear, disappear and re-emerge as new objects. The longer you stare, the more interesting things become. Familiar styles, everything from Greek classicism to Art Nouveau to newspaper comics, are oozed and infused with layers of meaning. Fonts follow their own rules, demanding two or three or a dozen tries to discern what they say.

That’s more to the point of “Visual Trips,” the assertion that these artists were communicating in a new mode, that they had a common language in their marks, that they were actually an authentic school of art. They may have been working commercially, producing lithographs that were stapled to telephone poles and taped to storefront windows, but they were collaborating as a group, purposefully developing something they intended would last.

Of course, it helps that they were working mostly for the same employers, most notably the legendary promoter Bill Graham, and hawking concerts at the same venues, either The Fillmore or the Avalon Ballroom. Concert producers saw the artists’ dreamy methods as a way of branding the business and encouraged their experimentation.

It also helps that there was a small corps of creators, most of whom knew one another and lived with each other’s output. Five artists in particular: Wes Wilson, Victor Moscoso, Stanley Mouse, Rick Griffin, and Alton Kelley.

Curator Scott Montgomery, a professor of Medieval and Renaissance art at DU, doesn’t hold back in his regard for their talents or his acceptance of their quirks, like the purposefully illegible words or drawing that varies in skill level. This is an exercise in elevation, moving a popular form into the world of fine art.

There are posters, but also a deep look at process. Mouse and Kelley’s collaborative offset lithograph for a 1966 Avalon Ballroom event is deconstructed, with the purple, green, black and red proofs displayed on the wall surrounding it.

The exhibit’s explanatory text, concise and easy to read, portrays the work as a product of its time, but also a leader of its moment. These artists defined what psychedelia looked like for anyone who walked the streets of San Francisco or bought albums by the Grateful Dead.

Montgomery wants us to understand just how broad the movement became. He gives due to peripheral artists in the show, like Bonnie MacLean and Lee Conklin, both serious talents. He includes posters for other events, like a 1967 production by the Pacific Ballet Company, to show how psychedelic ideas moved into the mainstream. In a few short years, those wavy lines would invade billboards and fashion and show up on lunch boxes and school notebooks.

As for the drugs, the exhibit simultaneously embraces them and distances itself. There’s no denying the influence of hallucinogenics — LSD in particular — on the artists’ imagination. The work can get wonderfully weird.

But Montgomery makes the point that these artists were drawing in this style before they dropped their first tab of acid and that this was serious business, not a Saturday in Golden Gate Park.

Drugs may have helped — well, let’s just assume they did — but they didn’t invent the imagination of these artists. They were products of their time, a line in history, and history is honoring their talents.

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Ray Mark Rinaldi is a Arts and Entertainment writer and critic at The Denver Post and a regular contributor to Reverb.